This application is based upon U.S. Provisional Patent Application Ser. No. 60/569,756 filed May 10, 2004.
This invention deals generally with farm machinery and more specifically with a speed or velocity control for such machines.
In the past two decades the use of electronic control systems in vehicles has seen a surge in development and applications. Due to economies of scale, the auto industry, with its large capacity, initially lead the way in the application of electronic controls on vehicles. Systems such as cruise-control, electronic engine management, climate control, and electronic transmissions are now common in road vehicles.
The velocity control, known as cruise-control in automobiles, has been present for quite sometime. Automobile drive trains exhibit non-linear dynamic behavior, particularly at lower speeds, but at higher speeds the action becomes more linear. Even with low speed non-linearity, velocity control has been successful for automobiles because cruise control is used almost exclusively in the higher speed ranges. However, the emerging technology of automated highway-systems calls for speed control systems that work over the full range.
In the last ten years manufacturers of agricultural machinery have also been developing and releasing more electronic control systems on their equipment to help agricultural producers implement precision agriculture, and the ultimate goal is fully automated machines. Although a variety of nonlinear and adaptive systems have been developed to address the non-linear control problems, the dynamics are somewhat different for the hydraulic drive trains of farm machines. Because of the larger mass of farm machines and the rougher terrain in which they operate, the control task in this work is much more difficult. An automated farm machine has many interacting subsystems, and must have several levels of control. The control objectives include vehicle motion, trajectory control, obstacle detection, and tool manipulation. To bring this technology into the agricultural market place the costs have to be reasonable for smaller quantities than are available in the automobile market. This requires that cost effective control systems be developed and implemented.
An automated farm machine relies on a database of information within an on-board computer to aid in decision making. Machinery with at least some level of automation is often required to make the best use of information in the database. An example of this is variable distribution technology or site specific crop management that can yield reductions in the quantities of agro-chemicals and fertilizer applied and can help reduce contamination of ground water and pollution of streams from run off.
One of the problems with automatic velocity or speed control for most agricultural equipment is the non-linear action of activating mechanisms, particularly solenoid valves within the hydraulic system that constitutes the drive train. A typical farm machine within which some automatic control systems are being implemented is a windrower, which is an agricultural machine for hay and forage preparation, crop harvesting, and crop residue processing. The performance of the hydraulic drive-train can vary considerably depending on the ground and crop conditions. When working in a field with varying ground and crop conditions the operator has to make many adjustments to maintain vehicle speed and loading. It would, therefore, be desirable to implement a velocity control system to reduce the number of adjustments the operator must make. This would allow the operator to concentrate more on other systems and processes. The objective of the velocity control system is to improve operator performance, and reduce fatigue. A control system that counteracts the non-linear characteristics of hydraulic controls would therefore be very beneficial for use with agricultural machines.